The present invention relates to an improved locking mechanism for plug-in electronic modules which are slidably mounted in grooves or ways in a chassis.
There is a constant demand for smaller electrical and electronic components, particularly in the aircraft and missile fields, as weight is of extreme importance. One concept of microelectronics which has been recently developed and which offers a great reduction in size and weight of electronic units is that of integrated circuitry which is formed on insulated bases such as glass, fused silica, or ceramic substrates. Integrated circuitry includes a number of active and passive components which are fabricated by one or more of a combination of several thin film deposition techniques onto a glass or ceramic substrate.
In order to reduce costs, expedite production, and provide a reliable electronic component, electronic plug-in modules have been developed which are capable of meeting various system requirements. One such plug-in module is shown in U.S. Pat. No. 3,243,660, entitled "Electronic Module Assembly", which issued Mar. 29, 1966, to Leonard J. Yuska and David P. Zimmerman. One concept of a standard hardware program is to have a plurality of modules which plug in a chassis to form an assembly and normally these plug-in modules slide in grooves or ways in the chassis and engage a mating female connector. These modules are closely assembled and dissipate a lot of heat which, if not removed, greatly affects component reliability.
Various attempts have been made to cool electronic assemblies and generally employ some type of cooling coil and fan assembly. One such device is shown in U.S. Pat. No. 2,187,011, entitled, "Cooling Means For An Electrical Apparatus", which issued Jan. 16, 1940, to Paul F. Braden. In one embodiment of this patent, a fan blows air over a cooling oil and the air passes successively through three shelves which support vacuum tubes and other electrical components. The disadvantage of such an arrangement, however, is that the first shelf receives cool air, which is heated by the electrical components, and the last shelf receives hot air and experiences little or no cooling effect.
In U.S. Pat. No. 3,942,586, entitled, "Cooling Arrangement For Flat Semiconductor Components", which issued Mar. 9, 1976, to Paul Fries, the inventor recognized a need for cooling all the mounted components. He stated that there is a need for an improved cooling arrangement for stacked flat semiconductors which can: (1) take advantage of the benefits of the heat pipe; and (2) in addition, provide adequate cooling to the semiconductors no matter what their location is within the column or stack. That is, the problem is to provide an arrangement in which cooling air of essentially the same temperature can flow over all the heat pipes in such an arrangement. The solution proposed was to axially align the semiconductor components, with the axes of the heat pipes of the cooling elements which are located one over the other, arranged so that they are rotationally displaced with respect to each other about the stack axis.
In U.S. Pat. No. 4,120,021, entitled, "Cooling System For Electronic Assembly", which issued Oct. 10, 1978, to Maurice Roush, there is described a system which provides a more efficient and higher capacity heat transfer from the circuit modules to the refrigeration system. There is provided a plurality of cooling bars associated with the chassis of the electronic apparatus and the cooling bars have a plurality of slots formed therein. The cooling bars are positioned adjacent one another and spaced apart a distance according to the width of the circuit modules. The circuit modules are provided with heat conducting flanges along the sides thereof which are adapted for fitting into the slots of adjacent cooling bars in heat conducting relation therewith. Clamping means are provided to clamp the flanges into tighter heat conducting contact with the slots. In a preferred embodiment, the clamping means comprises a plurality of camming surfaces attached to the face of the cooling bar adjacent the slots, and wedge blocks having second camming surfaces slidably positioned on the first camming surfaces adjacent the slots. Means are provided for moving the wedge blocks along the camming surfaces thereby forcing the wedge blocks against the heat conducting flanges and the flanges against the sides of the slots for maximum heat conducting contact.
Many plug-in modules of modern design now have wedge mechanisms at each end which are used to provide a good thermal interface between a module and the chassis. These units, however, generally require two separate tools for assisting in the insertion and removal of the plug-in module. One tool is of a wrench or screw driver type which supplies a mechanical advantage in operating the wedging mechanism. Another tool is of the type shown in U.S. Pat. No. 3,484,129, entitled, "Universal Extractor Tool", which issued Dec. 16, 1969, to Sherman G. Askren. This patent relates to an extractor tool for removing plug-in modules with a controlled force.
One disadvantage of using a separate tool for supplying a mechanical advantage in operating wedging mechanism is that there is no indicator or visual means to determine if the wedges have been moved to their desired position. Also, loose tools can be readily lost and frequently are not available when needed.